Indicating surface depressions in a material

ABSTRACT

An apparatus for indicating the surface depression, for example, softwood veneer, wherein light from a microscope illuminator is directed between a straightedge and a surface of the veneer passing in sliding contact underneath the straightedge, a silicon diode detects light reflected above a predetermined intensity from underneath the straightedge as an indication that the depth of the depression is above a minimum, and an electronic counter counts the number of such depressions per unit length of veneer. A marker attached to the counter applies a black mark to the veneer whenever a predetermined number of such depressions is exceeded per unit length, and a further marker may be used to mark the veneer with a red dot at each unit length.

United States atent [72] inventor Paul George Ottawa, Ontario, Canada [21] Appl. No. 859,965

[22] Filed Sept. 22, 1969 [45] Patented Nov. 9, 1971 [73] Assignee Canadian Patents and Development Limited Ottawa, Ontario, Canada [54] INDICATING SURFACE DEPRESSIONS IN A MATERIAL 4 Claims, 6 Drawing Figs.

[52] US. Cl 235/92 V, 235/92 R, 235/92 DN, 235/92 PE, 250/219 DF, 250/223 R, 356/237 Primary ExaminerMaynard R. Wilbur Assistant ExaminerRobert F. Gnuse Attorney-James R. Hughes ABSTRACT: An apparatus for indicating the surface depression, for example, softwood veneer, wherein light from a microscope illuminator is directed between a straightedge and a surface of the veneer passing in sliding contact underneath the straightedge, a silicon diode detects light reflected above a predetermined intensity from underneath the straightedge as an indication that the depth of the depression is above a minimum, and an electronic counter counts the number of such depressions per unit length of veneer. A marker attached to the counter applies a black mark to the veneer whenever a predetermined number of such depressions is exceeded per unit length, and a further marker may be used to mark the veneer with a red dot at each unit length.

[51] Int. Cl G06m 3/02, 006m 1/272 [50] Field of Search 235/92; 250/219 DF, 219 WE, 223; 356/237 [56] References Cited UNITED STATES PATENTS 3,096,443 7/1963 Laycak 235/92 DN I 27 1200 26 I I l I?) v AHA "1 PATENTEUunv 9 l97| SHEET 3 BF 3 VENEER SPEED (fpm) FIG.6.

INDICATING SURFACE DEPRESSIONS IN A MATERIAL This invention relates to an apparatus for indicating surface depressions in a material.

One of the major problems in, for example, peeling softwood veneer is excessive roughness caused by factors such as cross grain, eccentricity of annual rings, different densities of springwood and summerwood, and improper lathe settings. Roughness in veneer consists of elevations and depressions. The elevations appear on the loose side of the veneer, which is on the bottom side of the sheet as it is cut from a log and leaves the lathe. The depressions appear on the tight or topside of the veneer as it leaves the lathe. Depressions follow the general direction of the grain and vary in length from one quarter inch to over one inch. The perpendicular distance from the flat surface of the veneer to the bottom of a depression will hereinafter be referred to as the depth of depression.

Rough veneer is objectionable for the following reasons:

a. roughness in face veneer represents material which must be removed by sanding and is therefore wasted,

b. a rough veneer core may show through the thin face veneer of a finished panel,

c. rough veneer is conducive to poor glue bonds,

d. the excessive adhesive deposited in the depressions is wasted, may cause bleed-through in the face veneer, and in extreme cases causes steam blisters to form.

In other studies it has been found that the depth of depression most frequent in commercial Douglas fir veneer is about 0.010 inch and that the depth is rarely deeper than 0.070 inch. Depressions under 0.020 inch are not detrimental to the quality of a finished panel and so can be tolerated. Depressions over 0.020 inch are objectionable in the face or cross-band veneers, but deeper depressions can be tolerated in core veneers. Thus a device is needed to detect depressions of any depth which may range from 0.010 to 0.060 inch.

A single depression exceeding the established tolerance and occurring 2 or 3 times in each linear foot may not be serious, but a concentration of such depressions occurring in a linear foot may be objectionable. Therefore, in general, there is a need for a device which will respond to concentrations of roughness and not to isolated depressions.

Veneer is peeled at rates as high as 700 linear feet per minute at which speed it is impossible to detect roughness by eye. Only after the veneer has come to a standstill can the roughness be seen and by that time thousands of linear feet of rough veneer may have been produced. When the lathe operator is aware that roughness is excessive he may be able to reduce it by adjusting the lathe settings. In cases where roughness cannot be avoided, it would be a desirable thing to provide an apparatus which would detect and mark the rough areas of veneers for subsequent clipping and sorting.

It is one object of the present invention to provide an apparatus which will indicate the depths of surface depressions of a grained surface of a fibrous material.

The invention provides an apparatus for indicating surface depressions in a material, comprising a straightedge, means slidably mounting said straightedge in an upward direction for maintaining sliding contact between said straightedge and a portion of the surface of said material, with said straightedge extending across said surface depressions, a light source disposed to one side of said straightedge for directing a beam of light between the contacting surfaces of said straightedge and said material, a light intensity detecting device disposed on the other side of said straightedge for detecting any light reflected from said light source underneath said straightedge by a depression in said grained surface, and indicating means connected to said detecting device for indicating the number of times said reflected light is thereby detected per unit length of said material, when said reflected light is above a predetermined intensity, as an indication of the number of depressions having a greater depth than a predetermined minimum.

In the accompanying drawings which illustrate, by way of example, an embodiment of the invention,

FIG. I is a perspective view of an apparatus for indicating depressions in a grained surface of a veneer,

FIG. 2 is a sectional side view along "-1, FIG. I,

FIG. 3 is a block diagram of the electrical apparatus for use with the apparatus shown in FIG. 1,

FIG. 4 shows the pulse amplitudes of summerwood and springwood veneers, produced by the apparatus shown in FIGS. 1 to 3,

FIG. 5 indicates different results of the apparatus shown in FIGS. 1 to 3 for two different depths of depressions and for different veneer speeds, and

FIG. 6 is a graph showing the effects of different moisture contents of the veneer on the output from the apparatus shown in FIGS. 1 to 3.

Referring to FIGS. I to 3 there is shown a straightedge 1, means generally indicated by 2, for slidably mounting the straightedge l in an upward direction for maintaining sliding contact between the straightedge l and a portion of a grained surface 3 of a veneer 4, when the veneer 4 is disposed in contact with the working edge 5 of the straightedge l, with the straightedge 1 extending across the lengthwise direction x" of the grain. A light source 6 is disposed to one side of the straightedge 1, for directing a beam of light 7 along the grain between the contacting surfaces 5 and 3 of the straightedge I and veneer respectively. A light intensity detecting device 8, in the form of a glass tube encapsulated silicon diode, is provided on the other side of the straightedge l for detecting any light reflected underneath the straightedge l and along a depression in the grained surface 3. An indicating means generally designated 9, is connected to the device 8 The straightedge 1, upper wall 10 and means 2, forms a housing for the device 8 and in this embodiment is machined from a single piece. The straightedge l, which is 0.01 inch in thickness, is curved at both ends and the surface 5 is polished to slide freely on surface 3 of the veneer 4. The straightedge I is attached to plate member 11 which is 0.40 inch in thickness. The plate member 11 is slidably held in vertically grooved slideways l2 and 13 which form the means 2 for slidably mounting the straightedge l. The combined weight of the device 8 straightedge 1, plate member 11, light source 6, and a marker assembly 20 which is mounted on plate member II, is enough to ensure that the straightedge 1 remains in contact with surface 3 of the veneer 4.

A light source 6 is a microscope illuminator and is powered by an automotive type battery (not shown). The device 8 is energized by a 46 volt battery B] through switch S1 in a closed loop. The output is applied to an electronic counter I7 through a DC amplifier I5 and pulse shaper and discriminator 16. The electronic counter 17, in turn, controls the operation of solenoid valve 26a (FIG. I) of the marker system 20 through a pulse stretcher 18. A spotter and counter control 19 controls:

a. a compressed air operated spray type marker 20a of the marker system 20 to spot the surface 3 of the veneer 4 at l foot intervals with red dots through a microswitch 24 of control 19 and solenoid valve 26 of marker system 20; and

b. the electronic counter 17 to count the depressions which occur between each set of two consecutive red dots through microswitch 25 of control 19. The microswitch 25 stops, resets and starts the counter to count the number of depressions after each red dot is applied to surface 3 of the veneer 4.

The spotter and counter control 19 comprises a rubberrimmed disc 21 which is rotatably mounted in contact with the surface 3 of the veneer 4 has a circumference of 1 foot, and has an elevation on its side in the form of a bar 22 which operates microswitches 24 and 2S simultaneously.

The microswitch 24 actuates a normally closed solenoid valve 26 which introduces a controlled amount of red ink from an air pressurized cylinder 27 to marker 20a to spot the surface 3 of the veneer 4 at one foot intervals. As previously stated the microswitch 25, stops, resets and starts the counter when it is actuated.

The pulse stretcher l8 actuates the solenoid valve 26A to introduce a controlled amount of black ink from an air pressurized cylinder 27a to marker 20a to mark the surface 3 of the veneer 4 only when a preset number of depressions of a set minimum depth occur between each two consecutive red dots have been counted by the electronic counter 17.

The marker 20, and cylinders 27 and 27a are each connected to a compressed air source 23.

In operation the veneer 4 is moved at seven hundred feet per minute, in the direction of arrow Y, (FIG. l), and the light source 6 is energized. The light source 6, being a microscope illuminator, emits parallel rays of light which form the beam 7. The device 8 has the glass tube encapsulated silicon diode thereof arranged to receive light from the end only, that is reflected by the depressions in surface 3. The silicon diode has a dark resistance of 100 megohms, and when it is exposed to light its resistance drops according to the light intensity, and will drop almost to zero when exposed to a light intensity of a certain magnitude.

As the straightedge l rides over the surface 3 of the veneer 4, any depressions in the surface 3 will cause light to be reflected to the device 8 from the source 6.

As shown in FIG. 2 the intensity of reflected light is dependent upon the depth of the depression from which it is reflected, that is for a depression 0.02 inch in depth, designated 28, light is reflected from a lengthwise portion of the bottom of the depression, for a depression 0.04 inch in depth, designated 29, light is reflected from a lengthwise portion b" of the bottom of the depression, and for a depression 0.06 inch in depth, designated 30, light is reflected from a lengthwise portion 0 of the bottom of the depression. Thus the magnitude of the signal from the device 8 is an indication of the depth of the depression causing the reflection.

The signals from the device 8 are applied to the DC amplifier l which is used as a high impedance load across R and as an amplifier with, in this instance, a gain of three. The signal from the DC amplifier R5 is then applied to the pulse shaper and discriminator 16 which in this instance is a Schmitt trigger circuit. As a discriminator, which is the prime function of the pulse shaper and discriminator, it will only pass the pulses caused by depressions with a depth greater than any set minimum, and apply these pulses to the electronic counter 17.

As mentioned earlier, a single depression of a set minimum depth, which occurs once or twice in each linear foot of scanned veneer d is not objectionable, and so should be disregarded by the apparatus. When, however, the frequency of occurrence of depressions reaches or exceeds any predetermined number per linear foot of scanned veneer, they should be detected and marked. To this end the rubber rimmed disc 21 is rotated by the movement of the veneer 4 and, as previously stated, actuates the solenoid 26 to apply the red dots, at one foot intervals, and resets the counter 7, through the spotter and counter control 19, to count the depressions, of a predetermined minimum depth, between the red dots.

The display of the number of depressions that is indicated by the counter 17 is used to control the marker system 20 through the pulse stretcher 18, which incorporates a relay system. The display time of the number of depressions indicated between the red dots applied by the marker 26 is often shorter than the time required for a conventional 1 volt, 60 cycle solenoid valve 26a of the marker to respond. For this reason the device 8, which has a response time of 10 milliseconds, triggers the pulse stretcher and relay 1%, which in turn energizes the solenoid valve 26a and the marker 20, to release a spray of marker ink therefrom on to the veneer, when the predetermined number of depressions of minimum depth is indicated on the counter 17.

The marker 200 comprises a spray nozzle mounted about three-quarters of an inch above the veneer 1 at the scan line of the apparatus. An air flow is continuously applied through the nozzle and the marker ink is introduced therein by the solenoid valves.

The relay portion of the pulse stretcher and relay 18 may also actuate an audio and/or visual signal to the operator, or to any remote area.

The apparatus may also include means for automatically moving the portions of the apparatus, which are in contact with the veneer 4, away from the veneer 4, when there is a break in the flow of the veneer 4 or when the apparatus is not required to detect depressions in the veneer l.

The portion of the apparatus for applying the red dots, while useful for checking the apparatus, need not be included in the apparatus for use in a factory. If the portion of the apparatus for applying the red dots is included in industrial apparatus, it may only be used for checking the apparatus and then disconnected when the apparatus is found to be functioning in a satisfactory manner.

THE APPARATUS DESCRIBED WITH REFERENCE TO FlGS. ll TO 3 There are several factors which affect the accuracy of the apparatus. The more important of these and their effects are as follows:

A. Growth Rates The anatomical characteristics of springwood and summerwood of Douglas Fir have an effect on the light reflective properties which can be compared to the reflective properties of blotting paper and to those of writing paper respectively. Reflections from the rough surface of springwood occur in many directions for any one direction of incident light from the light source 6, and is said to be diffused. On the other hand reflections from the relatively smooth shiny surface of summerwood take place along a direction determined mainly by the direction of incident light from the light source 6, and is called regular. Therefore, if the device 8 is set at the same angle as the regular reflection, summerwood at the bottom of a depression would cause a stronger signal than would springwood. It is necessary therefore to set the device 8 in such an angular position that the summerwood is at a disadvantage in comparison to the springwood. The two types of wood reflect light vertically at a more equal rate, therefore, the device 8 is positioned, as shown in FIG. 2, perpendicular to the veneer surface 3, and the light source 6 is set sothat light beam 7 is directed at an angle of 45 degrees relative to the veneer surface and to the device 8.

The different reflective properties are illustrated in FIG 4 which is a display of pulses produced in the apparatus shown in FIGS. 1 to 3, by machined depressions of the same depth. The larger pulses were produced by those depressions which had summerwood at the bottom of the depression while the smaller pulses were produced by those depressions which had springwood at the bottom. Under these conditions the difference in pulse height represents the magnitude of error due to this factor and is estimated to be about I0 percent.

B. Veneer Speed Variation The pulses which are produced by depressions in veneer vary slightly in amplitude as the veneer speed changes. At very high speeds the duration of the pulse caused by a depression becomes comparable to the response time of the device 8. A study of the effect of the veneer speed on the pulse amplitude was simulated by cutting a set of twenty depressions varying in depth from 0.015 to 0.060 inch into a Douglas fir plywood disc. The disc was mounted on a shaft and rotated with a variahis speed motor while the detector scanned the plywood surface. The disc with the depressions, simulated rough veneer moving at speeds varying from 400 to 900 feet per minute. The pulses which were caused by the depressions were accurately measured with an oscilloscope.

The graphs in FIG. 5 were plotted 31 for the 0.015 inch depression, and 23 for the 0.060 inch depression. These results indicated that in both instances the change in amplitude of the pulses from the 0.015 in. 0.060 in. depressions due to a speed variation of 500 feet per minute, is z=0.35 volts, that is less than 6 percent. If the speed in a commercial veneer plant varied as much as 200 feet per minute the resulting variation in pulse amplitude would be less than 3 percent. This variation is insignificant when it is compared to the variation caused by the difference in the reflective properties of springwood and summenivood of Douglas fir veneer.

C. Veneer Moisture Content The reflective properties of freshly cut softwood veneer are affected to some extent by moisture content. When the moisture content is below fiber saturation point the wood is lighter in color and therefore reflects more light. Above the fiber saturation point the wood is darker and the reflective rate of softwood veneer decreases with increasing moisture content. it is seldom that the moisture content of Douglas fir heartwood exceeds 40 percent; it is usually in the range of 30 to 40 percent. FIG. 6 shows the results of tests made to determine the effect of veneer moisture content on the amplitude of pulses produced by depressions 0.03 inch deep. it can be seen that over the moisture content range of 3040 percent, the change on pulse amplitude is 3 percent, which is small compared with that caused by the difference in the reflective properties of Douglas fir springwood and summerwood.

Tests Made on a Douglas Fir Log A Douglas Fir log was peeled with lathe settings conducive to the production of rough veneer. The log was then scanned with all detector components in operation. The pulse shaper and discriminator 16 (HO. 3) was set to count only those depressions which were 0.020 inch deeper and the frequency of occurrence to be detected was set at depressions per linear foot.

The results from 185 linear feet are given in table A below. in this table the first column indicates the concentration of depressions expressed as the number per linear foot. For example, in column 1 0" means there was no depression equalling or exceeding the set minimum depth which occurred in a single occasion. Column 2 lists the number of occasions where the concentration was found by actual measurements. For example, in column 2 the number 83" represents the number of occasions in which there were no depressions of the set minimum depth per linear foot, while in column two of the number ll represents the number of occasions in which there were 10 depressions of the set minimum depth per linear foot. Column 3 illustrates the reliability characteristics of the device by indicating the number of occasions on which the marker 20:: marked the veneer 4.

TABLE A.TYPICAL RESULTS OF TESTS MADE ON A DO UGLAS-FIR LO G 0.020 inches and deeper (number per linear foot). iPstsna asiPy. 92 ma as-w lclaim:

1. Apparatus for indicating grain surface depressions in a material comprising a straightedge, means slidably mounting said straightedge in an upward direction for maintaining sliding contact between said straightedge and a portion of the surface of said material, with said straightedge extending across said surface depressions, a light source disposed to one side of said straightedge, for directing a beam of light along the grain and between the contacting surfaces of said straightedge and said material, a li ht intensity detecting device disposed on the other side of sai strarghtedge for detecting any light reflected from said light source underneath said straightedge along a depression, and indicating means connected to said detecting device for indicating only the number of times said reflected light is thereby detected when a predetermined minimum number of times is exceeded per unit length of said material, when said reflected light is above a predetermined intensity, as an indication of the number of depressions having a greater depth than a predetermined minimum.

2. Apparatus according to claim 1, wherein marking means is provided for marking said fibrous material at positions where said minimum number of times reflected light is detected by said detecting device is exceeded.

3. Apparatus according to claim 1, wherein marking means is provided for marking said fibrous material at said unit lengths, and said indicating means includes a marking means for marking said fibrous material between said unit length markings at positions where said minimum number of times reflected light is detected by said detecting device is exceeded.

4. Apparatus according to claim 1, wherein said detecting device is a glass tube encapsulated silicon diode, and indicating means has a DC amplifier for amplifying the output of said silicon diode, a pulse shaper and discriminator for indicating the output signals of said pulse shaper and discriminator when they are above a predetermined value, an electronic counter for counting the outputs from said pulse shaper and discriminator, and a spotter and counter control for receiving the output of said electronic counter and actuating said marking means of said detecting device t h i i 8 

1. Apparatus for indicating grain surface depressions in a material comprising a straightedge, means slidably mounting said straightedge in an upward direction for maintaining sliding contact between said straightedge and a portion of the surface of said material, with said straightedge extending across said surface depressions, a light source disposed to one side of said straightedge, for directing a beam of light along the grain and between the contacting surfaces of said straightedge and said material, a light intensity detecting device disposed on the other side of said straightedge for detecting any light reflected from said light source underneath said straightedge along a depression, and indicating means connected to said detecting device for indicating only the number of times said reflected light is thereby detected when a predetermined minimum number of times is exceeded per unit length of said material, when said reflected light is above a predetermined intensity, as an indication of the number of depressions having a greater depth than a predetermined minimum.
 2. Apparatus according to claim 1, wherein marking means is provided for marking said fibrous material at positions where said minimum number of times reflected light is detected by said detecting device is exceeded.
 3. Apparatus according to claim 1, wherein marking means is provided for marking said fibrous material at said unit lengths, and said indicating means includes a marking means for marking said fibrous material between said unit length markings at positions where said minimum number of times reflected light is detected by said detecting device is exceeded.
 4. Apparatus according to claim 1, wherein said detecting device is a glass tube encapsulated silicon diode, and indicating means has a DC amplifier for amplifying the output of said silicon diode, a pulse shaper and discriminator for indicating the output signals of said pulse shaper and discriminator when they are above a predetermined value, an electronic counter for counting the outputs from said pulse shaper and discriminator, and a spotter and counter control for receiving the output of said electronic counter and actuating said marking means of said detecting device. 